[en] The authors are currently engaged in a program to determine the potential of resonance ionization mass spectrometry (RIMS) for ultrasensitive isotopic measurements and for the determination of certain nuclear properties (e.g., spin and magnetic moment) of rare isotopes. The RIMS process has been under development for the past 5 yr or so as a technique for ultrasensitive elemental analysis. In RIMS, conventional mass spectrometry is combined with resonant laser ionization to provide sensitive, selective detection of elemental species. The resonance ionization process can achieve (by virtue of enormous resonance enhancement) nearly unit efficiency ionization of a selected elemental species. The mass spectrometer provides mass-specific (more precisely, mass-to-charge ratio specific) detection of the ion with near unit efficiency. Recently, RIMS was used to detect 1000 ⁸¹Kr atoms in a background of 10⁷⁸⁰Kr and ⁸²Kr atoms and 10¹² atoms of other elements. It has also provided part-per-billion sensitivity in the measurement of gallium in solid silicon